a. Field of the Invention
The instant invention relates to ablation devices, methods of using them, and steerable devices for use in medical treatments. In particular, the invention relates to devices used in conjunction with atrial fibrillation procedures and improvements related to the introduction of devices around the heart or at epicardial surfaces.
b. Background Art
A number of surgical procedures employ the use of steerable devices, such as catheters. In an atrial fibrillation treatment for ablating cardiac tissues, an alternative to the surgical incisions of the heart is the maze procedure, where transmural ablations of the heart are made within an ablation device. Such ablations may be performed either from within the chambers of the heart (endocardial ablation) using endovascular devices (e.g., catheters) introduced through arteries or veins, or from outside the heart (epicardial ablation) using devices introduced into the chest. Various ablation techniques have been used, including cryogenic, radiofrequency (RF), laser and microwave, to create elongated transmural lesions and block electrical conduction in the atrial myocardium. An advantageous use of transmural ablation rather than surgical incisions is the ability to perform the procedure on the beating heart without the use of cardiopulmonary bypass. Maintaining the proper positioning against the wall of a beating heart can also be difficult. Visualization of endocardial anatomy and endovascular devices is often inadequate and knowing the precise position of such devices in the heart can be difficult, resulting in misplaced lesions.
Epicardial ablation devices and methods useful for creating transmural lesions for the treatment of atrial fibrillation have been described in U.S. Pat. No. 7,052,493 to Vaska et al. (“Vaska”) and U.S. Pat. No. 6,971,394 to Sliwa et al. (“Sliwa”), both of which are hereby expressly incorporated by reference. Sliwa describes a method of forming a transmural lesion in a wall of the heart adjacent to the pulmonary veins by placing an ablation device through a thoracic incision and then through a pericardial penetration so that the ablation device is disposed in contact with an epicardial surface of the heart. Vaska describes an ablation device and system which may be used to wrap an ablation device around the pulmonary veins at an epicardial location.
Execution of a contiguous pulmonary vein (PV) isolation procedure can occasionally present considerable challenges to the physician. Difficulties in maneuvering the devices and passing them around anatomical structures, maintaining accurate placement on a beating heart, and avoiding unintended contact with other tissues mean that a high degree of physician skill and experience may be required in some circumstances. What are needed, therefore, are devices and methods which allow for precise introduction and placement of the ablation elements in PV isolation and linear left atrial ablations. More particularly, devices and methods which insure that ablation devices are properly placed or introduced for a PV isolation or mitral isthmus ablation procedure are desired.